Advice needed from the tuning gurus.

Hi, I'm having a devil of a job with the idle on my 06 GRiSO 1100, it has the Beetle 1100 map and a Quill can, when cold it has a very low speed tickover which stutters and when hot it will reach 950-1000. Things that I've done:- balanced throttle bodies at 60C at 3500rpm and tickover by opening only one air screw. TPS reset, 4.7 engine off and 7.1 running, presume difference is voltage higher when running. I ran the stepper test and the revs gradually increase to a nice level then back down again, does anyone know which way it's actuating on test, is the increase in revs the result of more or less air? Finally looking at the pipe it appears to be running rich, very black. I've tried CO trim but + or - 10 doesn't make much difference. What should I look at next? Thanks, Chris

Has the throttle stop screw been moved?

The TPS voltage shouldn't change when the engine is running. Have they been removed for cleaning at any point? Is there wear in the bores?

More air=leaner mixture= higher idle. Less air= richer mixture= lower idle.

Quote :

TPS reset, 4.7 engine off and 7.1 running, presume difference is voltage higher when running.

Fluctuations of the throttle value can occur at idle, but it's typically less than one degree. If it was reading, say, 4.9 or 5.1, that's not unusual.

7.1 is a problem. Most likely a bad TPS, or as Pete mentioned, has the throttle stop or linkage been messed with?

A quick check of the TPS can be made with GuzziDiag. With the engine off, slowly open the throttle and observe the throttle value. Does it rise "smoothly" or jump around? A check with an analogue voltmeter would be even more useful, but not many people have them these days.

Thanks both for your helpful replies. The bike has only done 12k miles so I hoping that general wear will be minimal. As far as the 'sacred screw' goes I've certainly not touched it knowing the pain it would cause, the paint still seems to be on it but I'll get a magnifying glass to double check.
As Pete mentions I presumed that the revs would rise with a leaner mixture and it appears that this is happening when I test the stepper motor.
The TPS reading is something that I need to sort first, correct me if I'm wrong but if the ECU sees 7.1 it'll deliver more fuel giving me a richer mixture and as the vanes/flaps are closed/idle position, will cause the idle revs to drop? I may have an analogue meter somewhere and appreciate that it would be better than the digital one for observing a gradual voltage change. The weird thing is that the reading jumps when starting the engine and there's no movement of the twist grip.
I should get a chance to investigate further over the weekend. Cheers, Chris

There's only about a 100 nanosecond difference in the pulse width between 4.6 & 7.1 at 1100 RPM in the main map. The actual real-time pulse that's calculated after all the corrections, which will also affect the stepper position, may be exactly the same. Don't know without comparing with another bike.

Have you tried holding the throttle closed with your finger while it's idling? The butterfly might flopping about.

Yup, to me this sounds like a 'Physical' problem rather than a mapping one.

The bike has only done 12,000 miles? It's now nearly 15 years old. I'd suggest at this point getting the TB's off for a really good scrub, then drain the tank completely and let it dry out. Change the filter just because and make sure the fuel pressure relief valve isn't rusty.

When you fire it up again run a dose of injector cleaner through it and re-tune it. The whole box and dice, tappets, TB balance, air filter check, cable adjustment etc. then ride it for a couple of tanks of petrol and re-check the tune.

It may change nothing but it's important to get the obvious shit out of the way first.

My two pennorth -
Many people overfill their Guzzi with engine oil and the overfilling causes oil blow-by to get into the airbox and throttle bodes.
When cleaning the throttle bodies remove the air-screws and clean them and that gallery. Also carefully remove the air temperature sensor from the airbox and clean any crud off the tip.

Thanks for all the advice, I'll let you know how I get on. First job will be to check that the 'screw' hasn't been fiddled with. Cheers Chris.

Just a quick update, the 'screw' has been tinkered with so before I go any further I'm going to get hold of a set of good used throttle bodies then I'll strip and clean everything. Will have to wait until my other bike hopefully get it's MOT at the weekend so that I've alternative transport for work, don't really want to use the car if I can help it.
Will update everyone in due course.

Pete is there no way of rescuing a set of throttle bodies after some helpful chappie has screwed with THE SCREW?

Yes and no. I'm cooking supper at the moment but give me a few hours and I'll try and explain.

Sorry, I forgot all about this question.

The answer is yes, and no. It really depends on what has been done to the TB's.

If it is just that the throttle stop screw has been moved, as long as the TPS hasn't been recalibrated you can just plug in Guzzidiag and wind the stop screw back until the value is back where it should be.

If though the TPS has been recalibrated then things get a lot more complicated and any remedial work a lot less easy and more likely accurate.

If the linkage rod, or even the bell crank screw, have been moved substantially then things get much, much less likely to be rectifiable.

Throw in wear in the throttle spindle bushes and you can just about forget it.

Michael, who is better at saving TB's than me, and I have both reached a point now where while we'll try to save molested TB's if things look grim we just say "Sorry, you need new TB's." The reason for that is you will never get them back to 'Like New' and even if we do get them a whole lot better than they were when the bike came in owners are frequently unhappy and go away thinking, (And telling their mates.) we're the world's biggest bastards yet unhung! Why would we want to put up with that shit? If people are reasonable? We'll try. But the distrustful sidelong glance brigade can just buy new TB's.

I just had to fit a new set to Todd's, (Bowraboy's) bike. Not because he was distrustful or stupid, simply because his set were unrecoverable. It now runs like a brand new bike.

If it ain't broke, don't fix it - however some shaved apes can't read or help themselves. However they fuck other peoples bikes in their ignorance and walk away "blameless". Arses.

Thanks Pete (and others) for all the helpful advice, I've now got my other bike on the road so will be able to spend time fettling the GRiSO. I will firstly do as you suggest, remove the throttle bodies and give them a good clean along with the stepper assembly etc and check the tune. If all this fails to improve things then I'll try to get hold of a good set of used bodies, new ones are crazy prices.
One thing that I have established is that the overall fuel consumption is pretty good, 50mpg, and that's when commuting, the problem is just the idle or lack of it.
Will let you know how it goes.

If it helps Chris
my tickover rose from 1050 with hiccups to a reliable 1200 after i cleaned the passages to and around the airscrews in the throttle bodies -

they were full of old black, gummy recycled oil

Many thanks for all the helpful advice, I finally got time at the weekend to give the bike some attention. I released the throttle bodies which on inspection were not too dirty but there was definitely a little oil and some black crap in them. These were treated to copious quantities of Carb/Injection Cleaner which cleaned them up a treat, also I gave a few good squirts down the stepper air feed tube, this looked as if it worked as fluid appeared through the ports in the TB's. Whilst I had good access I swapped the TPS for a new one.
On starting the bike it was stumbling on idle but a TPS reset instantly brought the revs up to around 1000, and this morning when starting ready to commute to work the revs were again around the 1000, great result. If the 'Screw' has been adjusted in it's past life then it can't have been by too much.
Now that the fuelling issues have been sorted it's onto the rear shock, any suggestions on how stop the 'bucking bronco' ride on anything other than a perfectly smooth road?
Cheers, Chris